The present invention relates to novel glycoside compounds, to physiologically active substance containing them as active ingredients, to a method for producing them, and to their uses. More particularly, the present invention relates to glucosides containing isomaltol as an aglycon, to physiologically active substances containing the glucosides as active ingredients, to a method for producing them and to their uses.
It is known that cultures of basidiomycete have properties of BRM (Biological Response Modifiers) such as immunopotentiation, immunological activation, or macrophage activation.
Also the present inventors have filed a patent application on an agent for recovering productivity of cytokines such as human monocyte interferon gamma (IFN-xcex3), or interleukin 12 (IL-12) using a culture of basidiomycete (a fungus belonging to Basidiomycetes) (Japanese Patent Application No. Hei 11-283223).
The physiological activities contained in such a culture of basidiomycete have been disclosed in xe2x80x9cWater-soluble ligninxe2x80x9d (Examined Japanese Patent Publication No. Hei 6-88909), xe2x80x9cComplex of cyctokinin based active substance composed mainly of polysaccharide and zeatin-related substancexe2x80x9d (Examined Japanese Patent Publication No. Sho 62-36009), novel polysaccharide substances (Japanese Patent Application Laid-open No. Hei 8-259602) and so forth. As shown in these applications, basidiomycete cultures may contain several types of physiologically active substances. However, none of the physiologically active substance has been identified by the structure in such a manner that the existence thereof can be unambiguously confirmed by instrumental analysis, in particular a spectroscopic method (including nuclear magnetic resonance or the like).
In conventional methods, plant tissue materials have been used, so that the cultures contain various types of organic substances. Furthermore, little information on the structure of target compounds is available. This makes it difficult to distinguish the fraction containing the target substance by instrumental analysis even if separations means such as column chromatography is used. Therefore, it has been difficult to efficiently isolate and produce the component having excellent physiological activity.
It is an object of the present invention to elucidate the structure of main substances from among the components that bring about the physiological activity contained in the basidiomycete cultures to which the present inventors have paid attention for a long time, to specify conditions for producing the substance efficiently, and to provide uses such as food, medicine and feedstuff utilizing the physiological activity of the substance.
The present inventors have made extensive studies with a view to solving the above-mentioned problems. As a result, they have found out that reacting a culture solution obtained by preliminarily culturing a basidiomycete with a reaction mixture obtained by reacting bran extracts with an enzyme gives rise to a substance having an increased physiological activity. This is in contrast to the conventional culture method of basidiomycete in a medium containing a plant tissue material. Also, the present inventors have identified the substance. The present invention has been achieved based on the discoveries.
That is, the present invention relates to novel substances having a physiological activity, method for producing them, and their use as set forth below.
1. A glucoside containing isomaltol represented by formula 
(I):
(wherein Sug represents a glucose residue or a sugar linkage composed of two or more glucose units) as an aglycon.
2. A glucoside according to 1 above, represented by formula (II): 
(wherein n is 0 or an integer of 1 or more).
3. A glucoside according to 2 above, wherein n is 1 to 20.
4. A glucoside according to any one of 1 to 3 above, wherein the glucoside is obtained by reacting a culture solution obtained by culturing a basidiomycete with a reaction mixture of a rice bran extracts solution and an enzyme, and then isolating the glucoside by column chromatography.
5. A 1-O-(2-acetylfuran-3-yl)-xcex1-D-glucopyranoside represented by formula (III): 
which corresponds to the formula (II) in which n is 0.
6. A physiologically active substance comprising a glucoside according to 1 or 2 above as an active ingredient.
7. The substance having a physiologically activity according to 6 above, wherein the physiological activity increases human cytokine inducing ability.
8. The substance having a physiological activity according to 7 above, wherein the cytokine is tumor cell necrosis factor (TNF-xcex1).
9. The substance having a physiological activity according to 7 above, wherein the cytokine is interferon-gamma (IFN-xcex3).
10. The substance having a physiological activity according to 7 above, wherein the cytokine is interleukin-2 (IL-2).
11. A method for producing a glucoside represented by formula (I): 
(wherein symbols have the same meanings as defined in 1 above) having a physiological activity, comprising the step of reacting a culture solution obtained by culturing a basidiomycete with a reaction mixture obtained by reaction between a rice bran extracts solution and an enzyme, and isolating the glucoside.
12. A method for producing a glucoside represented by formula (I) in 1 above, having a physiological activity, comprising the steps of reacting a culture solution obtained by culturing a basidiomycete with a reaction mixture obtained between a rice bran extracts solution and an enzyme, and isolating the glucoside by column chromatography using as an index a component showing (1) a peak attributable to methyl hydrogen of methyl ketone by 1H-NMR spectrum and a peak attributable to hydrogen atoms at the 4,5-positions of a 2,3-di-substituted furan ring characteristic of AB system, and (2) 6 peaks attributable to glucopyranose and 6 peaks attributable to isomaltol by 13C-NMR.
13. A food containing a substance having a physiological activity according to any one of 6 to 10 above.
14. A medicine containing a substance having a physiological activity according to any one of 6 to 10 above.
15. A feedstuff containing a substance having a physiological activity according to any one of 6 to 10 above.